Chemically modified anion exchange membrane and method of preparing the same

ABSTRACT

The present invention relates to a chemically modified anion exchange membrane and a method of preparing the same and, more particularly, an anion exchange membrane in which sulfonic acid groups in a perfluorinated sulfonic acid electrolyte membrane are substituted with anion conductive groups such as ammonium group, phosphonium group, imidazolium group, pyridinium group and sulfonium group, and a method of preparing an anion exchange membrane by chemically modifying sulfonic acid groups in a perfluorinated sulfonic acid electrolyte membrane.

TECHNICAL FIELD

The present invention relates to chemically modified an anion exchangemembrane and a method of preparing the same, and more particularly, to amethod of preparing an anion exchange membrane by modifying sulfonicacid groups (—SO₃ ⁻H⁺) of a perfluorinated sulfonic acid electrolytemembrane with various anion conductive groups and an anion exchangemembrane, which are chemically modified thereby.

BACKGROUND ART

An ion-exchange membrane refers to a polymer membrane that selectivelypermeates anions and cations and is classified into a cation exchangemembrane and an anion exchange membrane according to its chargecharacteristics, respectively. A cation exchange membrane has negativelycharged functional groups, permeates only cations by electricalattraction, and blocks the movement of anions by electrostaticrepulsion. In addition, an anion exchange membrane has positivelycharged functional groups, transports anions by electrical attraction,and blocks the movement of cations by electrostatic repulsion.

Such ion-exchange membranes should have excellent selective permeabilityand ion exchange capacity, low electrical resistance and diffusioncoefficient, excellent electrical properties, and low production costs.Particularly, ion-exchange membranes in the field of fuel cells or redoxflow cells require larger ion exchange capacity and better electricalproperties than conventional membranes.

However, when DuPont Nafion117, which is a commercially available anionexchange membrane, is used, since the crossover of ions in a batteryoccurs severely, self-discharge of the battery occurs and thus thebattery has low efficiency. In addition, the ion-exchange membranes usedas a separator in the water treatment field have to have excellentresistance to strong acid and base substances, and AMX known as arepresentative anion exchange membrane has excellent ion exchangecapacity and electrical property, but poor chemical resistance, therebyeasily reducing durability and efficiency.

Meanwhile, in Korean Unexamined Patent Application No. 10-2013-00255821,an ion-exchange membrane prepared by synthesizing 4-vinylbenzylchloride, styrene and 2-hydroxyethyl acrylate, amination andcrosslinking, and a method of preparing the same are disclosed, and inKorean Unexamined Patent Application No. 10-2014-0119479, a method ofpreparing an anion exchange membrane by converting a copolymercontaining a vinyl imidazole-based compound,trifluoroalkyl(meth)acrylate, and a divinylbenzene-based monomer into aquaternary ammonium compound and performing thermal treatment isdisclosed. However, since such a preparation method has complicatedsteps, production efficiency is lowered, and since the thickness of themembrane increases to reinforce the mechanical property or chemicalresistance of the ion-exchange membrane, ion exchange performance islowered.

For this reason, the development of anion exchange membranes is requiredto solve the difficulty in membrane formation due to low solubility,which is the unique characteristic of an anion conductive ionomer, ahigh resistance due to a large thickness, and low performance of ananion exchange membrane having a hydrocarbon-based main chain.

DISCLOSURE Technical Problem

The present invention is directed to providing a method of preparing ananion exchange membrane by substituting sulfonic acid groups (—SO₃ ⁻H⁺)in a perfluorinated sulfonic acid electrolyte membrane with variousanion conductive functional groups through chemical modification andthus may solve the difficulty in membrane formation due to lowsolubility, which is the unique characteristic of an anion conductiveionomer, and a high resistance due to a large thickness.

The present invention is also directed to providing an anion exchangemembrane which has stabilized electron density due to the introductionof a bridge group according to chemical modification and is improved inion conductivity and electrochemical performance.

Technical Solution

To solve the above-described problems, the present invention provides amethod of preparing an anion exchange membrane characterized bysubstituting sulfonic acid groups in a perfluorinated sulfonic acidelectrolyte membrane with ammonium groups, which are anion-conductivefunctional groups, the method comprising: a) chlorinating sulfonic acidgroups in a perfluorinated sulfonic acid electrolyte membrane; b)nitrating the chlorinated electrolyte membrane; c) aminating thenitrated electrolyte membrane; and d) activating the anion-conductivefunctional groups by treating the aminated electrolyte membrane underalkaline conditions.

The present invention also provides a method of preparing an anionexchange membrane, which are characterized by substituting sulfonic acidgroups in a perfluorinated sulfonic acid electrolyte membrane with otheranion-conductive functional groups, the method comprising: a)chlorinating sulfonic acid groups in a perfluorinated sulfonic acidelectrolyte membrane; b) introducing bridge groups to the chlorinatedelectrolyte membrane; and c) substituting the chlorine groups in thebridge group-introduced electrolyte membrane with anion-conductivefunctional groups, wherein the anion-conductive functional groups areselected from phosphonium group, imidazolium group, pyridinium group orsulfonium group.

The present invention also provides an anion exchange membrane in whichsulfonic acid groups in a perfluorinated sulfonic acid electrolytemembrane are substituted with anion-conductive functional groups,wherein the anion-conductive functional groups are selected fromammonium group, phosphonium group, pyridinium group, imidazolium groupand sulfonium group.

Advantageous Effects

Sincean anion exchange membrane is prepared by chemically modifyingsulfonic acid groups in a perfluorinated sulfonic acid electrolytemembrane according to the present invention, it can solve the difficultyin membrane formation due to low solubility, which is a peculiarcharacteristic of anion conductive ionomers, and high resistance due toa large thickness.

Generally, since commercialized anion-exchange membranes having ahydrocarbon-based main chain does not have a hydrophilic-hydrophobicphase-separation structure, it exhibits low performance, but in theperfluorinated polymer electrolyte membrane used in the presentinvention, the hydrophilic-hydrophobic phase separation structure issuitable for ion exchange, and thus it can exhibit high performance witha small thickness. However, fluorine of the ion-exchange membrane havinga perfluorinated main chain has high electronegativity such that anionconductive groups applied to the terminal becomes chemically unstable,and in the present invention, an electron density can be stabilized byintroducing bridge groups in chemical modification. In addition, theanion exchange membrane prepared according to the present invention hasa small thickness, excellent stability, and high anionic conductivityand electrochemical performance, and thus it can be applied in a varietyof industrial fields.

DESCRIPTION OF DRAWINGS

FIG. 1 is a Fourier transform infrared (FT-IR) analysis graph forconfirming reaction steps of Example 1 of the present invention.

FIG. 2 is a set of images showing hydrophilicity measured by reactionstep according to an example of the present invention.

FIG. 3 shows the densities of membranes prepared according to examplesand comparative examples of the present invention.

FIGS. 4 and 5 are the table and graph showing the OH⁺ ion conductivitiesof the anion exchange membranes prepared according to examples andcomparative examples of the present invention, respectively.

FIG. 6 is a diagram showing the hydrophilic-hydrophobic phase separationstructure of a perfluorinated ionomer and a hydrocarbon-based ionomer.

FIGS. 7 and 8 are the table and graph showing the area specificresistance of the anion exchange membranes prepared according toexamples and comparative examples of the present invention.

MODES OF THE INVENTION

The present invention will be described in further detail with referenceto examples and drawings as below.

A method of preparing an anion exchange membrane according to thepresent invention is characterized substituting sulfonic acid groups ina perfluorinated sulfonic acid electrolyte membrane with ammoniumgroups, which are anion-conductive functional groups, the methodcomprising: a) chlorinating sulfonic acid groups in a perfluorinatedsulfonic acid electrolyte membrane; b) nitrating the chlorinatedelectrolyte membrane; c) aminating the nitrated electrolyte membrane;and d) activating the anion-conductive functional groups by treating theaminated electrolyte membrane under alkaline conditions.

Another method of preparing an anion exchange membrane according to thepresent invention is characterized by substituting sulfonic acid groupsin a perfluorinated sulfonic acid electrolyte membrane with otheranion-conductive functional groups, in which the anion conductive groupsis selected from phosphonium group, imidazolium group, pyridinium groupand sulfonium group. The method includes a) chlorinating sulfonic acidgroups in a perfluorinated sulfonic acid electrolyte membrane, b)introducing bridge groups to the chlorinated electrolyte membrane, andc) substituting the chlorine groups in the bridge group-introducedelectrolyte membrane with anion-conductive functional groups,

The chemical modification of anion exchange membrane according to thepresent invention is characterized by introducing various types of anionconductive groups by varying reaction pathways as shown in ReactionSchemes 1 to 5 below.

In the present invention, modification may progress according toReaction Scheme 1, and specifically, the chemical modification of ananion exchanger may be performed according to a first step(chlorination, —OH→—Cl), a second step (nitration, —Cl→—NO₂), a thirdstep (amination, —NO₂→—NH₂), and a fourth step (alkaline treatment,—NH₂→—NH₃ ⁺).

In addition, in the present invention, modification may progressaccording to Reaction Scheme 2, and specifically, the chemicalmodification of an anion exchanger may be performed according to a firststep (chlorination, —OH→—Cl), a second step (introduction of a bridgegroup, —Cl→—C₆H₅Cl), and a third step (substitution the chlorine groupwith phosphonium group, —Cl→—PR₃ ⁺).

In addition, in the present invention, modification may progressaccording to Reaction Scheme 3, and specifically, chemical modificationof an anion exchanger may be performed according to a first step(chlorination, —OH→—Cl), a second step (introduction of a bridge group,—Cl→—C₆H₅Cl), and a third step (substitution the chlorine group withimidazolium group, —Cl→—C₃H₃N₂ ⁺).

In addition, in the present invention, modification may progressaccording to Reaction Scheme 4, and specifically, the chemicalmodification of an anion exchanger may be performed according to a firststep (chlorination, —OH→—Cl), a second step (introduction of a bridgegroup, —Cl→—C₆H₅Cl), and a third step (substitution the chlorine groupwith pyridinium group, —Cl→—C₅H₅N⁺).

In addition, in the present invention, modification may progressaccording to Reaction Scheme 5, and specifically, the chemicalmodification of an anion exchanger may be performed according to a firststep (chlorination, —OH→—Cl), a second step (introduction of a bridgegroup, —Cl→—C₆H₅Cl), and a third step (substitution the chlorine groupwith sulfonium group, —Cl→—SR₂ ⁺).

As a perfluorinated sulfonic acid electrolyte membrane that can be usedin the present invention, a perfluorinated sulfonic acid ionomerfree-standing membrane or a reinforced composite membrane includingporous supports may be used.

Specifically, as the perfluorinated sulfonic acid ionomer, for example,poly(perfluorosulfonic acid)s, sulfonic acid-containing-copolymerscomposed of tetrafluoroethylene and fluorovinylether, and their mixturesthereof, may be used, but the present invention is not limited thereto.

In addition, when a reinforced composite membrane are used as theperfluorinated sulfonic acid electrolyte membrane, porous supportsincluded in the reinforced composite membrane may be, for example,polymers such as polytetrafluoroethylene, poly(vinyldifluoroethylene),polyethylene, polypropylene, poly(ethyleneterephthalate), polyimide andpolyamide, but the present invention is not particularly limitedthereto.

Specifically, the chemical modification according to the presentinvention is described step by step as follows. First, the chlorinationstep may be performed by treating the perfluorinated sulfonic acidelectrolyte membrane with a solution containing one or more compoundsselected from the group consisting of SOCl₂, MeSO₂Cl, PCl₅, POCl₃, anddichloromethane (DCM), but the present invention is not limited thereto.Any solution that can chlorinate sulfonic acid groups may be used.

In addition, chlorination is preferably performed at 10 to 110° C., anda reaction time may be selectively adjusted depending on how much thechemical modification of sulfonic acid groups is needed, and generally,it is preferable that the reaction time be in a range of approximately30 seconds to 24 hours.

After the chlorination, reaction steps depend on the type of desiredanion conductive groups. Among these reaction steps, the introduction ofammonium groups as anion conductive groups includes nitration,amination, and alkaline treatment after the chlorination according toReaction Scheme 1.

Specifically, nitration may be performed by treating the perfluorinatedelectrolyte membrane undergoing chlorination with nitromethane ornitrobenzene solution, but the present invention is not limited thereto.Any solution that can substitute —Cl with —NO₂ can be used. Here, thenitration is preferably performed in the presence of sodium carbonate(Na₂CO₃) catalyst. In addition, the nitration is preferably performed at10 to 110° C., and a reaction time is suitably in a range of 30 secondsto 24 hours.

Next, the amination of the nitrated electrolyte membrane is performed.The amination may be performed by treating the nitrated electrolytemembrane, for example, with HCl aqueous solution, but the presentinvention is not limited thereto. Any solution that can substitute —NO₂with —NH₂ may be used. The amination is preferably performed at 10 to110° C., and it is preferable that the reaction time be in a range ofapproximately 30 seconds to 12 hours.

Afterward, to activate an anion conductive group, alkaline treatment isperformed. The alkaline treatment may be performed by treating theaminated electrolyte membrane with, for example, an aqueous solutioncontaining one or more compounds selected from the group consisting ofLiOH, NaOH and KOH, but the present invention is not limited thereto.Any solution that can substitute —NH₂ with —NH₃ ⁺ may be used. Thealkaline treatment is preferably performed at 10 to 110° C., and areaction time is preferably in a range of approximately 30 seconds to 24hours.

In addition, the chemical modification of sulfonic acid groups withammonium groups according to the present invention may further includewashing and drying after each of the chlorination, the nitration, theamination and the alkaline treatment.

Meanwhile, after the chlorination, the introduction of phosphoniumgroup, imidazolium group, pyridinium group or sulfonium group as anionconductive groups includes the introduction of bridge groups and thesubstitution of chlorine groups with anion conductive groups after thechlorination according to Reaction Schemes 2 to 5. Generally, fluorineof ion-exchange membrane having a perfluorinated main chain has highelectronegativity, and therefore, the anion conductive groups applied tothe terminal may be chemically unstable. To this end, in the presentinvention, as bridge groups are introduced in the chemical modification,an electron density may be stabilized.

Specifically, the introduction of bridge groups may be performed bytreating the chlorinated electrolyte membrane with chlorobenzene orbromobenzene solution, and thereby phenyl group is introduced as thebridge group. In addition, the introduction of bridge groups may beperformed at 10 to 130° C., and a reaction time is preferably in a rangeof 30 seconds to 24 hours.

Afterward, the substitution of chlorine groups with anion conductivegroups may be performed by treating the bridge group-introducedelectrolyte membrane with a solution including phosphonium group,imidazolium group, pyridinium group or sulfonium group. For example, thesubstitution may employ a solution including one or more compoundsselected from tris(2,4,6-trimethoxyphenyl)-phosphine, 1-methylimidazole,pyridine, 4-dimethylamino pyridine, dimethyl sulfide and methyl phenylsulfide, but the present invention is not limited thereto. Any solutionthat can be substituted with desired anion conductive groups may beused. The reaction is preferably performed at 10 to 80° C., and it ispreferable that the reaction time be in a range of approximately 30seconds to 24 hours.

In addition, the chemical modification of sulfonic acid groups withphosphonium groups, imidazolium groups, pyridinium groups or sulfoniumgroups according to the present invention may further include washingand drying after each of the chlorination, the introduction of bridgegroups, and the substitution with anion conductive groups.

Meanwhile, in the chemical modification according to the presentinvention, the reaction temperature and time ranges of each step may beappropriately adjusted as needed, but the present invention is notparticularly limited thereto. However, when each reaction is performedin temperature and time ranges lower than the above-mentionedtemperature and time ranges, each groups may not be sufficientlyconverted, and thus the performance of the prepared anion exchangemembranes may decrease, and when the reaction is performed intemperature and time ranges higher than the above-mentioned temperatureand time ranges, the cost may increase due to the decrease in processefficiency according to a long-term reaction. For this reason, thereaction is preferably performed in each condition range.

Meanwhile, the anion exchange membrane according to the presentinvention are an ion-exchange membrane in which sulfonic acid groups ina perfluorinated sulfonic acid electrolyte membrane are substituted withanion conductive groups, wherein the anion conductive groups areselected from ammonium group, phosphonium group, pyridinium group,imidazolium group and sulfonium group. In addition, anion conductivegroups of the chemically-modified anion exchange membrane according tothe present invention are preferably bound with —SO₂ groups in theperfluorinated sulfonic acid electrolyte membrane via bridge groupsselected from methyl group and phenyl group. Meanwhile, the OH⁻conductivity of the ion-exchange membrane substituted with anionconductive groups according to the present invention is in a range of0.001 to 0.3 S/cm, and the area specific resistance thereof is in arange of 0.0033 to 17.9 Ωcm², and thus the anion exchange membraneexhibits very excellent performance and properties.

Hereinafter, the present invention will be described in further detailwith reference to specific examples. The following examples are providedto help in understanding the present invention, but it should not beinterpreted that the scope of the present invention is limited thereto.

Example 1

Chlorination (the first step) in Reaction Scheme 1 was performed bystirring 5 g/mL of SOCl₂/dichloromethane at a speed of 400 rpm in anitrogen atmosphere at 40° C. and reacting Nafion117 (membranethickness: 175 μm), which is a perfluorinated sulfonic acidionomer-based electrolyte membrane, for 4 hours. After the reaction, theresulting product was washed with dichloromethane for 5 minutes anddried in a vacuum oven at 80° C. for 4 hours.

Subsequently, nitration (the second step) was performed by stirring anitromethane solution at a speed of 200 rpm in a nitrogen atmosphere at80° C., adding sodium carbonate as a catalyst at 20 wt % with respect tothe weight of the electrolyte membrane obtained after the first step,and reacting the chlorinated Nafion117 for 7 hours. Afterward, theresulting product was washed with deionized water for 3 hours and driedin a vacuum oven at 80° C. for 4 hours.

Amination (the third step) was performed by stirring 0.5 M HCl solutionat a speed of 200 rpm at 50° C., reacting the nitrated Nafion117 for 3hours, washing the resulting product with deionized water for 3 hours,and drying the resulting product in a vacuum oven at 80° C. for 4 hours.

Finally, alkaline treatment (the fourth step) was performed by stirring0.5 M KOH solution at a speed of 200 rpm at 50° C., reacting theaminated Nafion117 for 3 hours, washing the resulting product withdeionized water for 3 hours, and drying the resulting product in avacuum oven at 80° C. for 4 hours.

Example 2

Chlorination (the first step) in Reaction Scheme 2 was performed bystirring 5 g/mL of SOCl₂/dichloromethane at a speed of 400 rpm in anitrogen atmosphere at 40° C. and reacting Nafion117, which is aperfluorinated sulfonic acid ionomer-based electrolyte membrane, for 4hours. After the reaction, the resulting product was washed withdichloromethane for 5 minutes and dried in a vacuum oven at 80° C. for 4hours.

Subsequently, the introduction of bridge groups (the second step) wasperformed by stirring chlorobenzene solution at a speed of 200 rpm innitrogen atmosphere at 80° C. and reacting the chlorinated Nafion117 for12 hours. Afterward, the resulting product was washed with deionizedwater for 3 hours and dried in a vacuum oven at 80° C. for 4 hours.

Finally, substitution the chlorine groups with phosphonium group (thethird step) was performed by stirring a MeOH solution to which 30 wt %tris(2,4,6-trimethoxyphenyl)-phosphine (TTMPP) was added at a speed of200 rpm in a nitrogen atmosphere at 30° C., reacting the phenylchlorinated Nafion117 for 24 hours, washing the resulting product withdeionized water for 3 hours, and treating the resulting product with 1MKOH aqueous solution at a speed of 200 rpm at 50° C. to convert Cl⁻groups into OH⁻ groups. Afterward, the resulting product was washed withdeionized water for 3 hours and dried in a vacuum oven at 80° C. for 4hours.

Example 3

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that the introduction of a bridge group (the secondstep) was performed by reacting Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 10° C. for 24 hours,and the substitution the chlorine group with phosphonium group (thethird step) was performed by reacting the resulting product at 10° C.for 36 hours.

Example 4

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that the introduction of a bridge group (the secondstep) was performed by reacting the Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 130° C. for 30seconds, and the substitution the chlorine group with phosphonium group(the third step) was performed by reacting the resulting product at 80°C. for 30 seconds.

Example 5

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that and substitution the chlorine group withimidazolium group (the third step) of Reaction Scheme 3 was performed bystirring 30 wt % 1-methylimidazole-added 1-propyl alcohol at a speed of200 rpm in a nitrogen atmosphere at 30° C. and reacting Nafion117undergoing the introduction of a bridge group (the second step)described in Example 2 for 24 hours, washing the resulting product withdeionized water for 3 hours and treating the resulting product with 1MKOH aqueous solution at a speed of 200 rpm at 50° C. for 3 hours toconvert a Cl⁻ group into a OH⁻ group, and washing the resulting productwith deionized water for 3 hours and drying the resulting product in avacuum oven at 80° C. for 4 hours.

Example 6

An anion exchange membrane was prepared in the same manner as describedin Example 3, except that the introduction of a bridge group (the secondstep) was performed by reacting the Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 10° C. for 24 hours,and the substitution the chlorine group with imidazolium group (thethird step) was performed by reacting the resulting product at 10° C.for 36 hours.

Example 7

An anion exchange membrane was prepared in the same manner as describedin Example 3, except that the introduction of a bridge group (the secondstep) was performed by reacting the Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 130° C. for 30seconds, and the substitution the chlorine group with imidazolium groupwas performed by reacting the resulting product at 80° C. for 30seconds.

Example 8

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that the substitution the chlorine group withpyridinium group (the third step) of Reaction Scheme 4 was performed bystirring a 30 wt % pyridine-added n-butyl alcohol solution at a speed of200 rpm in a nitrogen atmosphere at 30° C. and reacting Nafion117undergoing the introduction of a bridge group (the second step) inExample 2 for 24 hours, washing the resulting product with deionizedwater for 3 hours, treating the resulting product with 1M KOH aqueoussolution at a speed of 200 rpm at 50° C. to convert a Cl⁻ group into anOH⁻ group for 3 hours, and washing the resulting product with deionizedwater for 3 hours and drying the resulting result in a vacuum oven at80° C. for 4 hours.

Example 9

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that the introduction of a bridge group (the secondstep) was performed by reacting Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 10° C. for 24 hours,and the substitution the chlorine group with pyridinium group (the thirdstep) was performed by reacting the resulting product at 10° C. for 36hours.

Example 10

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that the introduction of a bridge group (the secondstep) was performed by reacting Nafion117, which is the chlorinatedelectrolyte membrane prepared in the first step, at 130° C. for 30seconds, and the substitution the chlorine group with pyridinium group(the third step) was performed by reacting the resulting product at 80°C. for 30 seconds.

Example 11

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that a substitution the chlorine group withsulfonium group (the third step) of Reaction Scheme 5 was performed bystirring 30 wt % dimethyl sulfide-added MeOH at a speed of 200 rpm in anitrogen atmosphere at 30° C. and reacting Nafion117 undergoing theintroduction of a bridge group (the second step) in Example 2 for 24hours, washing the resulting product with deionized water for 3 hoursand treating the resulting product with 1M KOH aqueous solution at aspeed of 200 rpm for 3 hours at 50° C. to convert Cl⁻ group into OH⁻group, and washing the resulting product with deionized water for 3hours and drying the resulting product in a vacuum oven at 80° C. for 4hours.

Example 12

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that the introduction of a bridge group (thesecond step) was performed by reacting Nafion117, which is thechlorinated electrolyte membrane prepared in the first step, at 10° C.for 24 hours, and the substitution the chlorine group with pyridiniumgroup (the third step) was performed by reacting the resulting productat 10° C. for 36 hours.

Example 13

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that the introduction of a bridge group (thesecond step) was performed by reacting Nafion117, which is thechlorinated electrolyte membrane prepared in the first step, at 130° C.for 30 seconds and the substitution the chlorine group with pyridiniumgroup (the third step) was performed by reacting the resulting productat 80° C. for 30 seconds.

Example 14

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that Nafion117-PFM, which is a reinforced compositemembrane, was used as a perfluorinated sulfonic acid electrolytemembrane.

Example 15

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that Nafion117-PFM, which is a reinforced compositemembrane, was used as a perfluorinated sulfonic acid electrolytemembrane.

Example 16

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that Nafion117-PFM, which is a reinforced compositemembrane, was used as a perfluorinated sulfonic acid electrolytemembrane.

Example 17

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that Nafion117-PFM, which is a reinforced compositemembrane, was used as a perfluorinated sulfonic acid electrolytemembrane.

Example 18

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that Nafion117-PFM, which is a reinforcedcomposite membrane, was used as a perfluorinated sulfonic acidelectrolyte membrane.

Example 19

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that, in the chlorination (the first step),Nafion117, which is a perfluorinated sulfonic acid ionomer-basedelectrolyte membrane, was stirred in a 1 g/mL of SOCl₂/dichloromethanesolution at a speed of 800 rpm for 30 seconds.

Example 20

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the chlorination (the first step) wasperformed by stirring 5 g/mL of SOCl₂/dichloromethane at a speed of 800rpm at 10° C. and reacting Nafion117, which is a perfluorinated sulfonicacid ionomer-based electrolyte membrane, for 24 hours.

Example 21

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the chlorination (the first step) wasperformed by stirring Nafion117, which is a perfluorinated sulfonic acidionomer-based electrolyte membrane, in 1 g/mL of MeSO₂Cl/dichloromethanesolution at a speed of 800 rpm for 2 hours in a nitrogen atmosphere atroom temperature.

Example 22

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the chlorination (the first step) wasperformed by stirring Nafion117, which is a perfluorinated sulfonic acidionomer-based electrolyte membrane, in 5 g/mL of MeSO₂Cl/dichloromethanesolution at a speed of 400 rpm for 12 hours in an air atmosphere at roomtemperature.

Example 23

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the chlorination (the first step) wasperformed by stirring Nafion117, which is a perfluorinated sulfonic acidionomer-based electrolyte membrane, in 0.5 g/mL of PCl₅/POCl₃ solutionat a speed of 400 rpm for 12 hours at 80° C.

Example 24

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the chlorination (the first step) wasperformed by stirring Nafion117, which is a perfluorinated sulfonic acidionomer-based electrolyte membrane, in 5 g/mL of PCl₅/POCl₃ solution ata speed of 200 rpm for two hours at 110° C.

Example 25

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the nitration (the second step) was performedby reacting Nafion117, which is the electrolyte membrane chlorinated(the first step) according to Example 1, for 30 seconds in a nitrogenatmosphere at 110° C.

Example 26

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the nitration (the second step) was performedby reacting Nafion117, which is the electrolyte membrane chlorinated(the first step) according to Example 1, for 12 hours in a nitrogenatmosphere at 40° C.

Example 27

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the nitration (the second step) was performedby reacting Nafion117, which is the electrolyte membrane chlorinated(the first step) according to Example 1, for 24 hours in a nitrogenatmosphere at 10° C.

Example 28

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the nitration (the second step) was performedby stirring a 99.0% nitrobenzene solution at a speed of 200 rpm in anitrogen atmosphere at 80° C. and reacting Nafion117, which is theelectrolyte membrane chlorinated (the first step) according to Example1, for 7 hours.

Example 29

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the amination (the third step) was performedby reacting Nafion117, which is the electrolyte membrane nitrated (thesecond step) according to Example 1, for 30 seconds in a nitrogenatmosphere at 100° C.

Example 30

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the amination (the third step) was performedby reacting Nafion117, which is the electrolyte membrane nitrated (thesecond step) according to Example 1, for 6 hours in a nitrogenatmosphere at 50° C.

Example 31

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the amination (the third step) was performedby reacting Nafion117, which is the electrolyte membrane nitrated (thesecond step) according to Example 1, for 12 hours in a nitrogenatmosphere at 10° C.

Example 32

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the alkaline treatment (the fourth step) wasperformed by reacting Nafion117, which is the electrolyte membraneaminated (the third step) according to Example 1, for 30 seconds in anitrogen atmosphere at 110° C.

Example 33

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the alkaline treatment (the fourth step) wasperformed by reacting Nafion117, which is the electrolyte membraneaminated (the third step) according to Example 1, for 6 hours in anitrogen atmosphere at 80° C.

Example 34

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the alkaline treatment (the fourth step) wasperformed by reacting Nafion117, which is the electrolyte membraneaminated (the third step) according to Example 1, for 12 hours in anitrogen atmosphere at 10° C.

Example 35

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that the alkaline treatment (the fourth step) wasperformed by stirring 0.5 mol NaOH solution at a speed in a range of 200to 1000 rpm in a nitrogen atmosphere at 50° C. and reacting Nafion117,which is the electrolyte membrane aminated (the third step) according toExample 1, for 3 hours.

Example 36

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that Nafion 211 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 37

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that Nafion 212 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 38

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that 3M 725 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 39

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that 3M 800 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 40

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that a reinforced composite membrane (3M 725-PFM)was used as a perfluorinated sulfonic acid electrolyte membrane.

Example 41

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that Aquivion 72S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 42

An anion exchange membrane was prepared in the same manner as describedin Example 1, except that Aquivion 79S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 43

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that Nafion 211 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 44

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that Nafion 212 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 45

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that 3M 725 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 46

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that 3M 800 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 47

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that a reinforced composite membrane (3M 725-PFM)was used as a perfluorinated sulfonic acid electrolyte membrane.

Example 48

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that Aquivion 72S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 49

An anion exchange membrane was prepared in the same manner as describedin Example 2, except that Aquivion 79S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 50

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that Nafion 211 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 51

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that Nafion 212 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 52

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that 3M 725 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 53

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that 3M 800 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 54

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that a reinforced composite membrane (3M 725-PFM)was used as a perfluorinated sulfonic acid electrolyte membrane.

Example 55

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that Aquivion 72S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 56

An anion exchange membrane was prepared in the same manner as describedin Example 5, except that Aquivion 79S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 57

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that Nafion 211 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 58

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that Nafion 212 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 59

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that 3M 725 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 60

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that 3M 800 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 61

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that a reinforced composite membrane (3M 725-PFM)was used as a perfluorinated sulfonic acid electrolyte membrane.

Example 62

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that Aquivion 72S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 63

An anion exchange membrane was prepared in the same manner as describedin Example 8, except that Aquivion 79S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 64

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that Nafion 211 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 65

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that Nafion 212 was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 66

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that 3M 725 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 67

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that 3M 800 was used as a perfluorinated sulfonicacid electrolyte membrane.

Example 68

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that a reinforced composite membrane (3M 725-PFM)was used as a perfluorinated sulfonic acid electrolyte membrane.

Example 69

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that Aquivion 72S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Example 70

An anion exchange membrane was prepared in the same manner as describedin Example 11, except that Aquivion 79S was used as a perfluorinatedsulfonic acid electrolyte membrane.

Comparative Example 1

A 200-μm Neosepta-AHA reinforced electrolyte membrane consisting of ahydrocarbon commercially available from ASTOM was used.

Comparative Example 2

A 180-μm Neosepta-ACLE-5P reinforced electrolyte membrane consisting ofhydrocarbon commercially available from ASTOM was used.

Comparative Example 3

A 150-μm Selemion-DSV reinforced electrolyte membrane consisting ofhydrocarbon commercially available from AGC ENGINEERING was used.

Comparative Example 4

A 148-μm Selemion-ASV reinforced electrolyte membrane consisting ofhydrocarbon commercially available from AGC ENGINEERING was used.

Experimental Example 1 Comparison of FT-IR Spectra

Through FT-IR analysis, chemical modification was confirmed. As shown inFIG. 1, in a step by step FT-IR spectra for preparing an anion exchangemembrane using Nafion117 according to Example 1, after chlorination, theS—OH peak (1, 3418 cm⁻¹) disappeared and the S—Cl peak (2, 1421 cm⁻¹)was observed, and after nitration, the S—Cl peak disappeared and the N—O(4, 1575 cm⁻¹) and C—H (3, 2963 cm⁻¹) peaks were observed. Afterward, itcan be confirmed that, after alkaline treatment was completed followingthe amination, the N—O peak disappeared, and the N—H (5, 3456 cm⁻¹) peakwas observed.

Experimental Example 2 Measurement of Hydrophilicity

The change in chemical modification was examined by measuringhydrophilicity step by step in each example of the present invention,and as shown in FIG. 2, hydrophobicity according to the chemicalmodification of a sulfonic acid group with high hydrophilicity wasconfirmed.

Experimental Example 3 Measurement of Density

The membranes prepared in the examples and the comparative examples wereswollen in deionized water to equilibrium, and then densities werecalculated according to Equation 1 below. The result is shown in FIG. 3.

Density (g/cm³)=W/(l ₁ ×l ₂ ×T)  [Equation 1]

[In Equation 1, W: the weight of membrane (g), l₁: the width of membrane(cm), l₂: the length of membrane (cm), T: the thickness of membrane(μm)]

Experimental Example 4 OH⁻ Conductivity

The OH⁻ ion conductivity of the anion exchange membrane prepared by thechemical modification described in each example was measured. The OH⁻conductivity was calculated by Equation 2 below after measuring ohmicresistance or bulk resistance using a four point probe AC impedancespectroscopic method, and the result is shown in the table of FIG. 4below.

σ=L/RS  [Equation 2]

[In Equation 2, σ: OH⁻ conductivity (S/cm), R: Ohmic resistance ofpolymer electrolyte (Ω), L: Distance between electrodes (cm), S: Area inelectrolyte with constant current (cm²)]

As shown in FIG. 5, it can be confirmed that OH⁻ ion conductivities ofNafion117 AEM and Nafion117-PFM AEM, which are perfluorinated anionconductive polymer electrolyte membranes undergoing chemicalmodification according to examples of the present invention, weresignificantly improved compared to commercially availablehydrocarbon-based ionomer-based polymer electrolyte membranes describedin the comparative examples. FIG. 6 is a diagram showing thehydrophilic-hydrophobic phase separation structure of a perfluorinatedionomer and a hydrocarbon-based ionomer. As confirmed in FIG. 6, aperfluorinated ionomer-based anion exchange membrane having anestablished hydrophilic-hydrophobic phase separation structure exhibitsa higher performance than a hydrocarbon-based ionomer having aninsufficient structure.

Experimental Example 5 Area Specific Resistance

The area specific resistance of the anion exchange membrane prepared bychemical modification described in an example was calculated by Equation3 below with ion conductivity value, and the result is shown in thetable of FIG. 7.

R(Ωcm²)=T/σ  [Equation 3]

[In Equation 3, σ: OH⁻ conductivity (S/cm), T: the thickness ofion-exchange membrane (cm)]

In addition, as shown in the graph of FIG. 8, it can be seen that theperfluorinated anion exchange membrane prepared according to an exampleof the present invention exhibits significantly low area specificresistance and thus exhibits a higher electrochemical property than thehydrocarbon-based anion exchange membrane described in a comparativeexample.

1. A method of preparing an anion exchange membrane, which ischaracterized by substituting sulfonic acid groups in a perfluorinatedsulfonic acid electrolyte membrane with other anion-conductivefunctional groups, the method comprising: a) chlorinating sulfonic acidgroups in a perfluorinated sulfonic acid electrolyte membrane; b)introducing bridge groups to the chlorinated electrolyte membrane; andc) substituting the chlorine groups in the bridge group-introducedelectrolyte membrane with anion-conductive functional groups, whereinthe anion-conductive functional groups are selected from phosphoniumgroup, imidazolium group, pyridinium group or sulfonium group.
 2. Themethod of claim 1, wherein the perfluorinated sulfonic acid electrolytemembrane is a perfluorinated sulfonic acid ionomer free-standingmembrane or a reinforced composite membrane including porous supports.3. The method of claim 2, wherein the perfluorinated sulfonic acidionomer is selected from the group consisting of poly(perfluorosulfonicacid)s, sulfonic acid-containing-copolymers composed oftetrafluoroethylene and fluorovinylether, and their mixtures thereof. 4.The method of claim 2, wherein the porous supports of the reinforcedcomposite membrane are selected from the group consisting ofpolytetrafluoroethylene, poly(vinyldifluoroethylene), polyethylene,polypropylene, poly(ethyleneterephthalate), polyimide and polyamide. 5.The method of claim 1, wherein the chlorination is performed by treatingthe perfluorinated sulfonic acid electrolyte membrane with a solutionincluding one or more compounds selected from the groups consisting ofSOCl₂, MeSO₂Cl, PCl₅, POCl₃, and dichloromethane (DCM).
 6. The method ofclaim 1, wherein the introduction of bridge groups is performed bytreating the chlorinated electrolyte membrane with a solution includingchlorobenzene, bromobenzene, or their mixtures thereof.
 7. The method ofclaim 1, wherein the bridge group is phenyl group.
 8. The method ofclaim 1, wherein the substitution of chlorine groups withanion-conductive functional groups is to react the bridgegroup-introduced electrolyte membrane with a solution including one ormore compounds selected from tris(2,4,6-trimethoxyphenyl)-phosphine,1-methylimidazole, pyridine, 4-dimethylamino pyridine, dimethyl sulfideand methyl phenyl sulfide.
 9. The method of claim 1, wherein each of thechlorination, the introduction of bridge groups, and the substitution ofchlorine groups with anion-conductive functional groups is performed at10 to 130° C. for 30 seconds to 24 hours.
 10. The method of claim 1,further comprising washing and drying, after each of the chlorination,the introduction of bridge groups and the substitution withanion-conductive functional groups.
 11. An anion exchange membrane inwhich sulfonic acid groups in a perfluorinated sulfonic acid electrolytemembrane are substituted with anion-conductive functional groups,wherein the anion-conductive functional groups are selected fromphosphonium group, pyridinium group, imidazolium group and sulfoniumgroup.
 12. The anion exchange membrane of claim 11, wherein theanion-conductive functional groups are chemically bonded with —SO₂groups in the perfluorinated sulfonic acid electrolyte membrane viabridge groups.
 13. The anion exchange membrane of claim 12, wherein thebridge groups are selected from methyl group and phenyl group.
 14. Theanion exchange membrane of claim 11, wherein the anion exchange membranesubstituted with anion-conductive functional groups has OH-conductivityof 0.001 to 0.3 S/cm.
 15. The anion exchange membrane of claim 11,wherein the anion exchange membrane substituted with anion-conductivefunctional groups has area specific resistance of 0.0033 to 17.9 Ωcm².